The curing of monomeric materials to produce thermoset resins is well known in the art. In general, the polymerizable monomers have at least one and customarily more than one reactive group which serves as a site for a curing or crosslinking reaction. The resulting cured products are typically highly crosslinked, insoluble solids. There are some polymerizable monomeric materials which will cure upon application of energy, e.g., heat or UV light. In many if not most cases, however, the addition of a curing agent is necessary to allow the crosslinking reaction to proceed at an acceptable rate. The curing agents are catalytic or stoichiometric relative to the resin to the crosslinked. The stoichiometric curing agents, a term often applied to a curing agent which is employed in a substantial quantity relative to the resin, are the more commonly used and are typically multi-functional compounds having a plurality of reactive sites capable of participating in crosslinking reactions. A mixture of the resin and a curing agent, referred to as a thermosetting resin composition, is then cured by application of heat, with or without the presence of an accelerator which may be added to obtain a more acceptable rate.
The class of chemical compounds known as expoxies, epoxides or oxirane compounds has well established utility in the art as the precursor of thermoset resins. Such compounds are characterized by the presence within the molecule of at least one oxacyclopropane group, i.e., the ##STR1## group. The reactive oxygen-containing three-membered ring provides an active site through which polymerization takes place. Polyfunctional epoxides including diglycidyl ethers of dihydroxylic compounds or diglycidyl esters of dibasic acids are broadly known in the art as is the reaction of such epoxides with active hydrogen compounds such as polyfunctional acids or amines. The resulting polymeric products are thermoset resins of known commercial utility in adhesives, films and coatings. By way of a particular illustration, the diglycidyl ether of 2,2-di(4-hydroxyphenyl)propane, also referred to as biphenol A or BPA, is an epoxy compound of substantial commercial utility. It is marketed by Shell Chemical Company as EPON.RTM. 828 Resin and is also marketed by others.
The polyfunctional epoxides of cyclic structure are of particular importance because of the relatively high glass transition temperatures which their cured derivatives often exhibit. It would be of advantage to provide novel thermosetting resins which include resin components having a number of types of cyclic structure.